Height = Weight, that's ok, but Height + Light = Expensive, and $100 is not expensive in the tripod world. My initial reaction before I saw your price was to say get a set of carbon fibre legs, but this is now out of the price range.
I'm not sure exactly what you deem as heavy. I have a "heavy" tripod the Manfrotto 190ProB legs. I too have a curved spine but when extended out and held over a shoulder, or when using an appropriate shoulder strap the weight becomes less of an issues and I take mine hiking. It is a pain to carry without a strap so that's something you should definitely consider when looking for a tripod.